a light-duty railway with a gage smaller than standard (1,520 mm in the USSR).
Narrow-gage railways are built primarily to serve industrial enterprises, logging operations, and opencut and underground mines. In some countries certain sections of general-use railroads have narrow gages. Among the gages used are 1,000, 914, 750, and 600 mm. The standard width for surface narrow-gage railways in the USSR is 750 mm; up to 90 percent of all narrow-gage railroads have this gage. The main advantage of narrow-gage railways is their relative simplicity of construction, which is brought about by the smaller volume of earthworks required, the simpler and lighter superstructure, and, consequently, the lower initial capital investment compared to standard-gage railways. The disadvantages of these railways are lower throughput capacity, the necessity of transshipping freight at the junctions with standard-gage railways, the need for more locomotives and rolling stock (because of the smaller size of the trains), and the need for more service personnel.
Narrow-gage railways play an important part in the internal transportation of certain industrial regions and may be economical at low levels of freight turnover and for short shipping distances. Special diesel freight engines and high-capacity cars adapted for specific types of freight, such as timber, ore, and peat, are used on narrow-gage railways to improve economic efficiency.